Persistent Organic Pollutants (POPs)

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The Problem with POPs

Persistent Organic Pollutants (POPs) are man-made substances that take a long time to breakdown in the environment, and become widely distributed throughout water, soil, and air, even to places where they have never been used. When living organisms are exposed, POPs accumulate in their fatty tissue, a process known as bioaccumulation.

Furthermore, species higher in the food chain consuming such organisms develop even higher levels of POPs, a process known as bio-magnification.

So, although the environmental levels are low, POP concentrations in the fatty tissue of predator animals can be thousands of times higher.

An example is the biomagnification in polar bears of polychlorinated biphenyl substances (PCBs) and other persistent chemicals. The POPs travel long distances from developed countries to the polar regions in air currents, and then condense in seawater. The POPs concentrate in the fatty layers of algae and then magnify through fish and seals up the food chain to the polar bears, which suffer high concentrations of POPs and serious health effects [1].

Humans too are exposed to these chemicals in food and air. Also, many household products contain POPs, which are used as flame retardants or surfactants. Consequently, POPs can be found at measurable quantities in people.

Human exposure can lead to increased cancer risk, reproductive disorders, alteration of the immune system, neuro-behavioural impairment, endocrine disruption, genotoxicity and increased birth defects.

The production of some well-known POPs have been banned for years, but are still be found in the environment. There is also concern about newer chemicals that have not yet been assessed for persistence and bioaccumulation.

This article looks at the regulatory control currently in place to protect people and environment from the hazards of POPs.

Regulations controlling POPs

Because POPs travel across national boundaries, the United Nations facilitated the Stockholm Convention [2], named after the city in which the was adopted, that became effective in 2004 and is updated regularly. The Convention obliges signatory countries to bring in measures to eliminate or restrict the manufacture and use of well-known POPs.

The EU fulfils the requirements of the Stockholm Convention through the POPs Regulation (2019/1021) [3].

Substances listed in Annexes to this Regulation are pretty much banned, except for some substances in exceptional circumstances such as closed-system, site-limited intermediates, manufacture and use under strictly controlled conditions. Any waste must be destroyed. There is also an exemption for laboratory use, for example in research of environmental contamination.

The list of substances comprises some insecticides, flame retardants, and wood treatments. POPs often contain multiple carbon–halogen (fluorine, chlorine, or bromine) bonds, which are resistant to microbial or hydrolytic breakdown, and give them their persistence in the environment.

The durability of POPs is often the property that makes them desirable, for example in long-lasting, water-repellent coatings, or in electrical components.

Because of the number and position of halogens may differ in the molecule, several POPs are ‘families’ rather than a single substance, eg polychlorinated biphenyls (PCBs), which can complicate detection in the environment.

Other POPs such as polychlorinated dioxins and polycyclic aromatic hydrocarbons (PAHs) are not intentionally produced, but can be formed during combustion processes, particularly incineration of chemical wastes, and their release should be monitored.

PBT and vPvB in REACH

The REACH Regulation (1907/2006) [4] is the central EU Regulation for discovering and reporting the hazards of chemicals. Suppliers of chemicals at greater than 10 tonnes/year are obliged to conduct a chemical safety assessment (CSA) to include as part of the registration dossier.

This assessment includes evaluation of the substance as ‘persistent, bioaccumulative and toxic’ (PBT) or ‘very persistent, very bioaccumulative’ (vPvB). The criteria for PBT and vPvB are given in the REACH Regulation, Annex XIII. Persistence is defined as having a freshwater half-life of > 40 days. To qualify as bioaccumulative, the bioconcentration factor is >2000. So PBT and vPvB substances share common environmental persistence and bioaccumulation with POPs.

PBTs and vPvBs are considered ‘substances of very high concern’ (SVHCs), and are subject to the REACH Authorisation. Such substances are listed in Annex XIV of the REACH Regulation, and can only be used after a sunset date if ECHA gives specific authorisation to an applicant for a particular process. Such an authorisation requires the applicant to demonstrate that:

  • socio-economic benefits of the use outweigh the risk to human health or the environment
  • there are no suitable alternative substances or technologies.

So, the POPs Regulation ensures that internationally known problem POPs are banned or restricted in use, while REACH acts to screen newer chemicals for these hazards.

Case study: Per- and Polyfluoroalkyl Substances (PFASs)

Per- and polyfluoroalkyl substances (PFAS) are a family of substances that have received much attention in recent years, owing to the persistence and toxicity of some PFASs.

PFASs have multiple carbon–fluorine bonds that are resistant to environmental breakdown, and so persist in the environment.

PFASs are used as surfactants, and are repellent to water, grease and dirt, and so have been used in:

  • Carpets, clothing, textiles and upholstery
  • Paper and packaging, including food packaging
  • Non-stick cookware
  • Water repellent sprays and polishes
  • Fire-fighting foams
  • Hydraulic fluids
  • Electronic equipment and components
  • Construction products and metal plating
  • Pesticides (as active ingredients and additives)

Workers are exposed during manufacture of goods that incorporate PFASs, or where PFASs are used extensively such as in fire-fighting. Members of the public are generally exposed to lower concentrations through contact with treated materials, or through the environment.

The best known examples of PFASs are perfluorooctanoic acid (PFOA) and perfluorohexane-1-sulphonic acid (PFOS). These substances are listed in the Stockholm Convention and the EU POPs Regulation. As such, they have been phased out from industrial production, except for specific uses, but still persist in the environment.

The Stockholm Convention, and the POP and REACH Regulations lists PFOA and related compounds, so that they are restricted in manufacture and import to specific uses, where it cannot easily be replaced.

These best-studied PFASs are known to accumulate in humans, and can lead to adverse health outcomes, including effects on the immune system, cancer, and hormone disruption.

In response to these restrictions, manufacturers developed a new generation of PFAS substances, that were intended to be less harmful. However, following investigation, several of the new substances have shown to possess similar properties and hazards.

Perfluorobutane sulfonic acid (PFBS) and its salts, and other poly-fluorinated substances, have recently been identified as SVHCs, and included on the Candidate List for inclusion into Annex XIV or REACH.


There are various legal processes for banning manufacture and import, or restricting the use of POPs.

Some POPs are a complex family of substances, and as such are less suited to simple regulatory actions, that requires precise identification of substances in order to simplify enforcement.

There is legitimate concern that the regulatory process for identifying POPs and ensuring action to prevent harm to people and the environment is too lengthy. Regulators are ‘playing catch up’ with fast moving manufacturing. Manufacturers may be replacing POPs with new products that are similarly hazardous.

As a result of historical POP use, and slow moving regulation, people and the environment are likely to suffer the effects from POPs for years to come. 


[1] Pollutants in the Arctic environment are threatening polar bear health;; 5 January 2017. [back]

[2] Stockholm Convention on Persistent Organic Pollutants (POPS); United Nations Environment Programme; 2017. [back]

[3] Regulation (EU) 2019/1021 of the European Parliament and of the Council of 20 June 2019 on Persistent Organic Pollutants (Recast); Official Journal of the European Union; L 169/45;  25 June 2019. [back]

[4] Regulation (EC) No 1907/2006 of the European Parliament and of the Council of 18 December 2006 concerning the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) (as amended). [back]

Alchemy Compliance has 22 years of regulatory experience with industrial chemicals, in EU REACH Registration, safety data sheet compilation (EU, US, and beyond), and chemical hazard assessment. Contact us for more information.